Large vehicles used in industrial applications such as at mine sites use large tyres which are very expensive, wear out quickly and are subject to damage from cuts and penetrations. Tyre chains are used to increase traction, protect and prolong the life of these tyres, which has been particularly important during recent years where there has been a shortage of such tyres.
The tyre chains that are currently used comprise a number of chain links connected by welded chain rings usually between two and four chain links per chain ring to provide an array of chain rings and links between these chain rings. Some of the chain links are ground engaging, and provide traction with the ground and need to incorporate the required wear material to continually perform this function.
The current practice is to use butt-welded chain rings of circular cross-section as the joining mechanism to assemble the chain. The use of butt welding results in a raised protrusion across a portion of the chain ring as a consequence of the welding process. The presence of this raised protrusion can hamper and or otherwise interfere with movement or rotation of the chain ring relative to the chain links when in service. This can reduce chain ring rotation and result in wear points forming on the chain ring at the specific points where the chain links contact the chain rings. Furthermore, wear is not evenly shared around the entire circumference of the chain ring.
Localised ring point wearing causes rapid dimensional expansion of the overall tyre chain assembly which then requires varying continual manual service adjustments so that the tyre chain assembly continues to stay within tension specification and correct running position on the tyre: this takes repeated servicing, time and effort. Eventually the whole tyre chain needs to be removed from the wheel, shortened and refitted to enable it to reach its end of service life or be replaced.
In addition, once the chain ring wears to the extent that the wearing extends past the centre line of the ring cross section at these focused ring wear points, a further rapid acceleration of wear results due to the reduction of actual surface area contact between the ring and the link engagement, thus increasing the surface load and wear rate.
The use of butt welding also places limitations on the dimensions that can be utilised for the component dimensions directly affecting area of the engagement surface between the chain link and chain ring as extra chain ring material length is required to facilitate the actual welding process of the ring during assembly of the chain assembly and the dimensions of the chain links are limited at the point where they are attached to the ring because they need to be bunched together to facilitate welding of the ring and also a further portion of the ring length is sacrificed for the welding process to take place. All these limitations imposed on the component dimensions increase the rate of wear between the link and the ring at the points where the chain link and chain ring engage.
The rate of wear dictates the rate at which the tyre chain tension needs to be manually adjusted, and also the service life of the tyre chain.
The materials that can be used for the chain ring are also limited by the need to use a welding process.
In certain applications it is critical that the tyre chain manufacturer needs to produce tyre chains that can be fitted onto wheel assemblies that are restricted in circumference due to clearance restrictions on the machines the wheels will be fitted to, such as the machines mudguards, framework and componentry. An important factor when producing chain links incorporating ground engaging wear material is the ratio between the height of the wear material portion compared to the overall height of the link. The current use of butt welded rings and the resulting raised protrusions on the ring surfaces around the weld area in the tyre chain assembly means that link cavities that contain the rings are generally enlarged to encourage welded ring rotation resulting in lower ratio of wear material height for a given link height.
Once the whole tyre chain is assembled then the whole tyre chain assembly has to undergo a heat treatment, quenching and tempering process, but, because the rings and links are constructed of different materials and also comprise varying mass and dimensions, there is a compromise in the whole process.
Any final processes are also limited, such as the application of performance enhancing treatments, shipping/storage preservatives, most surface coatings or product visual enhancements, can only be done once the tyre chain has been welded into an assembly and heat treated.
Welding processes during chain construction are hazardous, physically demanding, labour intensive, energy expensive and have extensive health and safety implications because of the heat, noise, dust, toxins, by-products and the like that are produced as part of the process. Tyre chain assemblies currently in use can be in excess of 5000 kg.
The process of welding and assembling the tyre chain requires repeated movements of the assembly, it is physically demanding and time consuming, and in larger applications chains need to be done in multiple sections which are then joined together with non-rotating rings. The life of the chain is also dictated by the life of the weakest or most worn component and often an end of service life chain will have a large number of rings and links which are still capable of being returned to service. Current welded tyre chain design places high costs and severe restrictions on the re-use of any salvageable components or sections of the scrapped used assembly.
The current practice of utilising welded rings for assembling chains means that chain assembly component specifications and chain assembly dimensions are set to prior to chain assembly manufacture and importers, dealers, distributors and service centres have to pre-empt demand for sizes and quantities and also stock chain assemblies to suit many different sizes of tyres and applications. There are significant costs and delays when ordering non-stocked or custom-built chains from tyre chain manufacturers, importers or dealers.
The present invention seeks to provide a tyre chain that addresses or at least partially ameliorates one or more of the problems discussed above.